Hello Alex, Paul, Markus and the rest of the small VLF group,
Indeed, a great achievement, one of the things i will look back to, when
my live comes to an end some day.
Thanks to Alex/RN3AUS for building up his VLF equipment in the garden
near Moscow, and for going there to take the daily files! Exemplary!!!
Thanks to Paul for his work, here the EbNaut software/decoder which
works perfectly on VLF. I no other mode we would have reached that result!!
Thanks to Markus/DF6NM for writing/providing useful tools for Windows
operators, here the add.exe program which allowed a weighted stacking of
the files.
But we must not forget to think about Wolf/DL4YHF for writing his great
SpecLab software, which is used and has been used by the most VLF
operators since the beginning! SpecLab was used here on the tranmitter
site to generate a stable frequency and phase, even correcting phase
changes of the antenna system (caused e.g. by rain or by temperature
changes of the coil or by soundcard glitches or or or). SpecLab has also
been used to get the necessary accuracy of the RX frequency in the
countryside as well as perfect timing.
We were quite lucky! Alex told me he will go to the graden to collect
the daily txt files on monday, thus i decided to run a 11th
transmission. Actually 'only' 10 transmissions were planned. No chance
of a decode with just 10 days.
Patience is essential and it is another good example to never give up
trying to do the 'impossible' things!
A plain carrier would have been easier because one can see something
building up after a much shorter time. But a message which is suddenly
decoded is much more fascinating :-) I lisented the song several times
last evening :-)
The files were scaled/normalised by the square of the amplitudes, as
suggested by Markus some time ago, i.e. kn[dB]= 2*20*log(U1/Un), where
U1 is the amplitude of the first recorded day.
I tried linear scaling of the files and got a decode too, so the
difference is very small.
Without daily amplitude scaling there was no decode.
In one day (10th), the QRN was very high, so the amplitude was scaled
down quite much (-4.4 dB). But even when leaving out this worst day,
there was no decode.
The set of data is very well suited to play with the add.exe tool by
Markus. Unfortunately i have no Linux computer which had enough RAM to
try to get results with Linux. Otherwise a decode may have happened
earlier, when using the -a parameter.
The last 5 days were quite quiet. Maybe a 12th transmission on a quiet
night would allow to get the decode after 'just' 6...7 days. But this
information is unknown as long as there is no decode of course.
The 6470 Hz experiments are no completed here for some time. The grabber
windows have been changed to 5170 Hz already. Last night i added more
turns on the coil. Now there are 4 buckets fully wound with 0.25 mm
enameled Cu wire. I checked the resonance frequency, i can tune down to
5364 Hz now. About 140 mH missing. Today i will buy another bucket and
start to wind a 5th bucket. A first carrier will soon appear at 5170 Hz.
The show must go on :-)
73, Stefan
Am 18.10.2017 18:25, schrieb Alex K:
Hello VLF!
I am glad to report that the 16-char message of Stefan on 6470.1 is
successfully decoded nr Moscow. The stacking of 11 copies of
transmission with accurate weight summation was required. Stefan the
first has achieved successful decode from my files. Then with his
councils it was succeeded to make it also to me. My big
congratulations to Stefan! Excellent work and is a little good luck
:-). Also huge gratitude to Markus for the excellent utility add.exe
and of course to Paul for magnificent ebnaut!
73 de rn3aus/Alex
PS all files are here
http://rn3aus.narod.ru/ebnaut-16ch-all-files-decoded.zip
ebnaut-rx V0.7a
input file C:\EbNaut\16char\sum-all-w.wav
sample rate 0.342935 per second
rx frequency 6470.1
file start time 2017-10-15 15:43:32.290
polynomial 16K21A
crc size 19
number of chars 16
block size 115
symbol period 20.000
number of symbols 2160
list length 868865
start offset 998.574
freq offset 0.000000
cores 1
skipped 997.273536 seconds to start
initial reference phase -37.2
---------------------------------------------
found YELLOW SUBMARINE
list rank 746119
reference phase 180 180 180 180
carrier S/N 19.25 dB in 23.1 uHz, -27.11 dB in 1Hz, -61.09 dB in 2.5kHz
carrier Es/N0 -14.10 dB
carrier Eb/N0 -0.35 dB
info bit period 473.68 seconds
symbol error rate 852/2160 = 39.444 %
Es/N0 from symbol errors -14.4 dB
Eb/N0 from symbol errors -0.7 dB
Shannon capacity 9.9 bits/hour
Shannon efficiency 76.7 %
symbols file C:\EbNaut\16char\sum-all-w-symbols.csv
elapsed 126 seconds
1
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